Answer:
20hours
Step-by-step explanation:
Jack can complete the painting in 30hours. The fraction he can paint per hour is thus 1/30
Trainee can complete the painting in 45hours, the fraction he can paint per hour is 1/45
If they are working together, the fraction that can paint in an hour is :
1/45 + 1/30 = 5/90 = 1/18
Now we know they can paint 1/18 of the room in an hour, the number of hours needed to completely paint the room is thus 1/1/18 = 18 hours
Rounding up answer to the nearest tenth is 20hours